Turkish police on Friday arrested 21 academics for "terror propaganda," referring to a petition denouncing Turkish military operations against Kurdish rebels in southeastern Turkey that has drawn the ire of President Recep Tayyip Erdogan, AFP reported.

In an early morning raid on their homes, police arrested the academics from the University of Kocaeli, near Istanbul.

The arrests came after prosecutors launched a massive investigation into over 1,200 academics from 90 Turkish universities, on accusations of "insulting the state" and engaging in "terrorist propaganda" by signing the petition.